1. Field of the Invention
The present invention relates to an image forming process and a printed article, and particularly to a process for forming an image having excellent image properties on a surface of a base material which has a high heat resistance of at least 150.degree. C., but has no ink absorbency.
2. Related Background Art
As processes for forming images on base materials such as ceramics such as earthenware, porcelain and stoneware, glass, plastics, and metals, which are not absorbent of liquid ink components, there have heretofore been a direct printing process in which printing is performed directly on these base materials, and a process of bonding a synthetic resin film, on which an image has been printed in advance, to the surfaces of these base materials to form an image thereon.
The former printing process is generally performed by gravure printing or offset printing. However, printing presses used in these printing processes are expensive, and the processes are required to fabricate a plate according to the desired pattern. Therefore, it has been hard to say that this process is suitable for small-quantity printing. A process in which an image is directly formed on a base material by an ink-jet recording system without fabricating a plate is also performed in part. Under the circumstances, this process is however applied only to printing of lot numbers on products and simple characters up to the present, and the color is also limited to a single color. When it is intended to print a color image by an ink-jet recording system on the surface of a base material having no ink absorbency, overlapped inks remain as ink droplets on the base material because the base material has no ink absorbency, so that fine color mixing is prevented, and boundaries between different colors become indistinct. In addition, the scratch resistance and wear resistance of the formed image are insufficient because printing is conducted directly on the base material. Namely, it has been difficult to form any bright color image excellent in scratch resistance and wear resistance directly on the surface of a base material having no ink absorbency by the ink-jet recording system.
On the other hand, the latter process is a process of bonding an image-printed synthetic resin film to the surface of a base material having no ink absorbency to form an image thereon, but offers a problem of adhesion between the image-printed film and the base material. Troubles such as peeling of the film have been often caused.
As a process for solving these problems, Japanese Patent Publication No. 47-51734 discloses a process in which an ink-receiving layer composed of a synthetic resin film is formed on the surface of a base material having no ink absorbency in advance, an image-printing sheet, on which an image containing a sublimate dye (disperse dye) has been formed, is laid on the synthetic resin film, and the printing sheet is then heated to sublimate the dye so as to transfer only the dye to the synthetic resin film on the base material, thereby forming an image on the resin film. Besides, as a process for forming an image containing a sublimate dye on a printing sheet, it is disclosed in Japanese Patent Publication No. 60-8959 to use an ink-jet recording system.
Specific examples of such receiving layers for disperse dyes as described above are disclosed in Japanese Patent Application Laid-Open Nos. 52-5843, 5-309956 and 6-143792. According to Japanese Patent Application Laid-Open No. 52-5843, however, fiber is intended for a base material, and so the principal object in view is to keep the hand feeling of a finished textile good. Therefore, any receiving layer having high mechanical strength such as high scratch resistance cannot be obtained. In Japanese Patent Application Laid-Open Nos. 5-309956 and 6-143792, it is described to use, as materials for the formation of receiving layers, polyester resin compositions having resistance to various stains which form the cause of irregularity of images formed. These resin compositions are believed to be excellent as materials for the formation of receiving layers for sublimate-transfer image-receiving paper. The sublimate-transfer image-receiving paper is generally used in recording systems such as a sublimate transfer system and a melt transfer system and attaches importance to recording speed. Therefore, as sublimate dyes used, those low in sublimation temperature are in use. On the other hand, when an image containing a disperse dye formed on an image-printing sheet is transferred to heat-resistant base materials such as pottery, glass, plastics and metals, it is desirable that the transfer be performed at a temperature as high as possible to effectively diffuse the disperse dye into the receiving layer. Namely, when the sublimate transfer is performed under such conditions, it is possible to form a bright and high-color density image, which conforms to the image on the image-printing sheet, on the surfaces of the base materials such as pottery and glass. When the transfer of the image is performed under such conditions, however, there has been problems that the receiving layer composed of the polyester resin composition as described above is softened, so that a situation that a mark of the image-printing sheet is left on the base materials in the form of irregularities, or that the image-printing sheet is not separated from the base materials in the worst case may be brought on.
When the use situation of image-printed articles obtained in the above described manner is considered, severe criteria as to properties of the images such as mechanical strength, light fastness, stain resistance and chemical resistance are not very required of displays and the like used indoors. When the printed articles are intended for building materials which are used outdoors, for example, external wall materials and floor covering materials, considerably severe criteria as to the properties of the images are required of them. Even when the printed articles are used indoors, it is necessary to take the prevention against the generation of mildew on the printed articles into consideration in the case where they are intended to use in places easy to generate dew condensation, such as bathroom and wall covering materials.
Further, there is described in Japanese Patent Application Laid-Open No. 51-116287 a process to add a new function to a printed article after conducting textile printing by sublimate transfer to a receiving layer. In this method, a flameproofing treatment is conducted by applying an overcoat layer to polyester fibers printed by the sublimate transfer. However, Japanese Patent Application Laid-Open No. 51-116287 does not describe anything about the improvement in mechanical strength, light fastness, stains resistance and chemical resistance. As materials for the formation of the overcoat layer, those containing a non-aqueous solvent in plenty are generally often used because of their good properties. When the liquid overcoat materials containing such a solvent in plenty are used, however, a disperse dye penetrated into the receiving layer has slightly exuded in some cases. Although the amount of the dye exuded is slight, it is conspicuous at the contour part of an image when the background of the image is white. Therefore, there has been a problem that a clearness of the image has been impaired.